How do I set up Qmail to accept incoming messages only from the EuropeanMX servers?

To limit the delivery of incoming messages in Qmail to the servers of EuropeanMX, please follow the steps below:

Qmail (TCPServer)

If you use Qmail in conjunction with tcpserver, you can add the following rule under /etc/tcp.smtp so that all incoming connections are accepted by EuropeanMX.

=delivery.antispamcloud.com:allow,RELAYCLIENT=''

Qmai (Inetd)

If you run Qmail as an inetd service using tcp-env, the entire configuration of SMTP access is done from the following files: /etc/hosts.allow and /etc/hosts.deny. Do not forget to add your own SMTP clients to /etc/hosts.allow.